# Happy Pi Day 2014! Everything You Need To Know About Annual Math Event

03/14/2014 02:58 pm ET

Today is the 26th celebration of National Pi Day, and the festivities are already underway.

Pi is an irrational number that expresses the ratio of a circle’s circumference to its diameter. You knew that, right? But you might not know that Pi Day was conceived back in 1988 by physicist Larry Shawn of San Francisco’s Exploratorium science museum.

Since that time, celebrations of Pi Day -- which happens to coincide with Albert Einstein's birthday -- has spread across the nation.

Why celebrate pi on March 14? Simple. Pi is commonly abbreviated to 3.14, and those digits are the same ones used to represent the fourteenth day of the third month. Got that?

Next year there will be a special twist, since the date -- 3/14/15 -- matches up with the first five digits of pi: 3.1415 (though the 5 would really be rounded to six).

How will you celebrate Pi Day? You could spend it reciting as many of its digits as possible (but you'll have a hard time measuring up to Chao Lu, a Chinese man who recited pi to 67,890 decimal places back in 2005). Then again, maybe you'd prefer simply to take advantage of some of the celebrations taking place today.

Museums in Boston, Seattle, San Francisco and many others cities are offering educational Pi Day events for kids and adults, CNN reported. In Chicago, there's a 3.14-mile walk.

Pizza Hut, Sbarro, and Jamba Juice, are offering Pi Day promotions and deals.And restaurants in the Philadelphia area are offering discounts and deals on pi-related desserts, according to Philly.com.

For more on Pi Day, check out Piday.org or the comprehensive Pi Day blog on The Huffington Post. In the meantime, celebrate with us, and have a slice of your favorite pie before the day is done.

14 Pictures Of Pies, Because It's Pi Day, Get It?

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Pi Day National Pi Day 3.14